| Popis: |
Some mechanistic aspects of yeast flocculation are reviewed, including among others its phenomenology, thermodynamics and kinetics, the mechanism of contact, Brownian motion of a yeast cell, the morphology of a floc, and the probabilistic collision of unequals. A model for visualising homotypic cell-cell interactions is presented. Called the Velcro model, it proposes that wall-wall connections are mediated and stabilised by hooks and loops, both located on either wall. The quasi-equilibrium in yeast flocculation is presumed to be due to the interchange of free cells (slipping into and out of the shallow secondary minimum of the potential energy curve) with the floe population by attaching to and detaching from the surfaces of flocs. Cells in the core of a floc, securely hooked to one another in the deep primary minimum, are less mobile and more stable to deflocculation. They have more cell connections and are provided with protective cover from erosive hydrodynamic forces on the floc surface. |
